Objective To observe the effects of electroacupuncture(EA) penetration needling on Toll-like receptors 4/myeloid differentiation factor 88/nuclear factor-kappa B(TLR4/MyD88/NF-κB) signaling pathway in rat synovium and the serum-related inflammatory factors

so as to explore the mechanism of EA penetration needling on synovial inflammation in rats with knee osteoarthritis(KOA). Methods SD male rats were randomly divided into sham-operation group

model group

EA+penetration needling group

and conventional EA group

with 16 rats in each group. The rats model was prepared by anterior cruciate ligment transection and these rats were forced to exercise for 8 weeks after operation. After successful modeling

in the EA+penetration needling group

the needles were inserted at “Dubi”(ST35) “Neixiyan”(EX-LE4)

and at “Xuehai”(SP10) “Liangqiu”(ST34) on the right hind limb

towards each other

5-8 mm in depth

respectively. In the conventional EA group

the needles were inserted at ST35 and EX-LE4 on the right hind limb

obliquely

at 30° angle to the skin

3-5 mm in depth; and were inserted at SP10 and ST34 on the right hind limb perpendicularly

3-5 mm in depth. In these two groups

electric stimulation was operated with dense-disperse wave

2 Hz/10 Hz in frequency and 0.5-1.5 mA in intensity

retained for 20 min in each treatment. The treatment was given once daily

10 days as 1 course of treatment

and 2 courses were required at the interval of 2 days. After the intervention

the knee joint effusion was observed by musculoskeletal ultrasound; the contents of IL-1β

IL-6 and TNF-α in serum were determined by ELISA; the morphological changes in the synovium were observed after H.E. staining; the positive expression of NF-κB p65 in the synovial membrane was detected by immunohistochemical method; the expression levels of TLR4

MyD88

TRAF-6 and NF-κB p65 proteins in the synovial membrane were determined by Western blot. Results Compared with the sham-operation group

in the model group

the knee joint effusion was obviously increased

the synovial lining cells were distributed irregularly

the cells were disarranged

the pannus was formed largely

and a great number of the inflammatory cells were infiltrated; the contents of serum IL-1β

IL-6 and TNF-α

the positive expression of NF-κB p65

the protein expression levels of TLR4

MyD88

TRAF-6 and NF-κB p65 in the synovial tissue were increased(P<0.05). Compared with the model group

the knee joint effusion was reduced

the synovial lining cells were proliferated

a small number of the inflammatory cells were infiltrated

and the pannus was formed lightly; the contents of serum IL-1β

IL-6 and TNF-α

the positive expression of NF-κB p65

the protein expression levels of TLR4

MyD88

TRAF-6 and NF-κB p65 in the synovial tissue were lower(P<0.05) in the EA+penetration needling group and the conventional EA group. In the conventional EA group

the knee joint effusion was increased

the synovial lining cells were proliferated

the inflammatory cells were infiltrated largely

and the pannus was formed increasingly; the contents of serum IL-1β

IL-6 and TNF-α

and the protein expression levels of TLR4

MyD88 and NF-κB p65 in the synovial tissue were increased when compared with the EA+penetration needling group(P<0.05). Conclusion The EA+penetration needling can significantly relieve the synovial inflammatory reaction and the knee joint effusion in KOA rats. The mechanism is probably related to down-regulating the downstream inflammatory cascade through inhibiting the transduction of TLR4/MyD88/NF-κB signaling pathway.